Abstract
ABSTRACT Maize is one of the species with greater genetic diversity among cereals and possibly the most diverse crop species known. Accessing this variability is essential for maize breeding, allowing breeders to achieve progress of yield increasing, overcome environmental challenges or deal with pests and diseases. Among the maize diseases, southern rust is one of the most important, causing significant losses in yield and presenting severe epidemics worldwide. In the present study, the AFLP technique was applied to analyze population structure and genetic diversity among 145 tropical maize inbred lines, and to test for preliminary evidence of association between AFLP markers and the reaction to southern rust. Disease severity was evaluated in two crop seasons and the accessions were genotyped through AFLP using four primer combinations. The clusters obtained based on the Jaccard genetic distance and Ward’s hierarchical clustering and those achieved by structure simulations had high concordance and were capable of establish two big clusters, one predominantly of common maize and another of popcorn. The association analysis was performed using four different statistical models. The more complete model containing both population structure and genetic relatedness narrowed the number of significant associations, demonstrating its importance to control false associations. A total of 19 significant marker associations were identified from which three (EactMctg18, EactMctg205, EactMctg169) are interesting candidates for further investigations.
Highlights
Maize (Zea mays L.) is one of the species with greater genetic diversity among cereals
Maize southern rust severity was scored in the diversity panel of 145 inbred lines across two crop seasons, with two replications in each environment
If we consider the frequency distribution of the severity performing class scores as proposed by Fantin (1997), we can see the variability of the association panel for the resistance to southern rust
Summary
Maize (Zea mays L.) is one of the species with greater genetic diversity among cereals. The huge diversity is shown by more than 350 races and multiple varieties, which carry many distinct characteristics (Vigouroux et al 2008), allowing the worldwide crop growing in various environmental conditions (Ranum et al 2014). The conservation and identification of the genetic diversity remaining within the germplasm pools of crop species are crucial for the breeding process. Despite the large genetic diversity of maize, the popcorn germplasm has a narrow genetic base (Ziegler 2001). This lack of diversity is a serious problem in breeding programs and can implicate the capacity of yield increasing, overcome environmental challenges or even in deal with pests or diseases
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